This disclosure is directed to optical media and more specifically to a method and system for recording data on and reading data from an optical medium such as compact disks.
Compact disks are well known in both the audio and video field. The term xe2x80x9ccompact diskxe2x80x9d herein refers generally to optically readable media, playable in CD players and/or computer CD drives, and typically carrying audio and/or video program material and includes both non recordable CDs and recordable CDs.
One technical problem addressed herein is that in addition to commercially available compact disks players, both as standalone devices and drives installed in computers, compact disk writers (xe2x80x9cburnersxe2x80x9d) are now commercially available. These writers accept a suitable data stream and write the data onto a recordable compact disk. An example is the Hewlett-Packard CD-Writer Plus 8100i CD-RW drive which installs in a standard personal computer drive bay, and which connects to the hard drive IDE connector in such a computer. Other versions connect to the computer SCSI or parallel port. CD writers also operate as CD players. Such writers now cost only about $400.00, and typically are sold bundled with suitable software, such as Adaptec""s Easy-CD Creator, which enables copying of a CD or other data (e.g., from a hard drive) to a recordable CD.
Since the material on a compact disk is typically in digital form, a copy of a compact disk contains all of the program material (user data) of the original. This of course encourages unauthorized copying, typically of copyrighted program material such as games, movies, etc., using such CD writers.
Furthermore, a CD recorded using standard data formats can be read or played by any commercially available CD player or CD-ROM drive. This can lead to the unauthorized usage of CDs, whether they be originals or illegal copies, by anyone with a commercially available CD player or CD-ROM drive.
Therefore, a need has arisen for a recording and playback system and method for optical media such as compact disks that addresses the disadvantages and deficiencies of the prior art. In particular, a need has arisen for a recording and playback system and method with a simply generated proprietary data format which is unreadable by standard compact disk players and CD-ROMs.
Accordingly, an improved method for recording data on an optical medium is disclosed. In one embodiment, the method includes receiving and encoding a first set of data frames by a CIRC encoder to generate a second set of data frames. A control byte is then added to each of the second set of data frames to generate a third set of data frames. The third plurality of frames of data are received and encoded at an EFM encoder to generate a section comprising a plurality of Channel frames. The control byte of a sequentially first one of the third set of data frames is replaced with a SYNC 0xe2x80x2 byte selected from the following group: 00000000001000, 00000000001001, 00000000010000, 00000000010001, 00000000010010, 00001000000000, 00010000000000, 00100000000001, 01001000000000, 10001000000000, and 10010000000000. The control byte of a sequentially second one of the third set of data frames is also replaced with a SYNC 1xe2x80x2 byte selected from the same group. The SYNC 1xe2x80x2 byte is different from the SYNC 0xe2x80x2 byte, and the SYNC 0xe2x80x2 and SYNC 1xe2x80x2 bytes are selected such that at least one of the following conditions is met: (a) the SYNC 0xe2x80x2 byte is not equal to 00100000000001, and (b) the SYNC 1xe2x80x2 byte is not equal to 00000000010010. The section is then recorded on the optical medium.
In accordance with another aspect of the present invention, an optical medium recording system is disclosed. The system includes a CIRC encoder that receives and encodes a first set of data frames to generate a second set of data frames. A control block adds a control byte to each one of the second set of data frames to generate a third set of data frames. An EFM encoder receives the third set of data frames and encodes selected portions of the third set of data frames to generate a section comprising a plurality of Channel frames. The EFM encoder also replaces the control byte of a sequentially first one of the third set of data frames with a SYNC 0xe2x80x2 byte selected from the following group: 00000000001000, 00000000001001, 00000000010000, 00000000010001, 00000000010010, 00001000000000, 00010000000000, 00100000000001, 01001000000000, 10001000000000, and 10010000000000, and replaces the control byte of a sequentially second one of the third set of data frames with a SYNC 1xe2x80x2 byte selected from the same group. The SYNC 1xe2x80x2 byte is different from the SYNC 0xe2x80x2 byte, and the EFM encoder also selects the SYNC 0xe2x80x2 and SYNC 1xe2x80x2 bytes such that at least one of the following conditions is met: (a) the SYNC 0xe2x80x2 byte is not equal to 00100000000001, and (b) the SYNC 1xe2x80x2 byte is not equal to 00000000010010. A recording mechanism receives the section and records the section on the optical medium.
In accordance with yet another aspect of the present invention, a method for reading data from an optical medium is disclosed. The method includes locating a section of data by scanning the optical medium for a SYNC 0xe2x80x2 byte and a SYNC 1xe2x80x2 byte, the SYNC 0xe2x80x2 and SYNC 1xe2x80x2 byte each being selected from the following group: 00000000001000, 00000000001001, 00000000010000, 00000000010001, 00000000010010, 00001000000000, 00010000000000, 00100000000001, 01001000000000, 10001000000000, and 10010000000000, the SYNC 1xe2x80x2 byte being different from the SYNC 0xe2x80x2 byte. The section of data is then read from the optical medium.
An advantage of the present invention is that a proprietary data format similar to a standard data format may easily be generated. Another advantage of the present invention is that the proprietary data format may not be read or copied by standard CD playback and copying systems.